The option you put there only affects Magnum Break's direct damage. The bonus damage is hardcoded, you can only set the duration in skill_cast_db: //-- SM_MAGNUM 7,0,0,0,2000,10000,2000 The code for the elemental damage bonus is in battle.c
if (sc && sc->data[SC_WATK_ELEMENT] && (wd.damage || wd.damage2)) {
// Descriptions indicate this means adding a percent of a normal attack in another element. [Skotlex]
int64 damage = battle_calc_base_damage(sstatus, &sstatus->rhw, sc, tstatus->size, sd, (is_skill_using_arrow(src, skill_id)?2:0)) * sc->data[SC_WATK_ELEMENT]->val2 / 100;
wd.damage += battle_attr_fix(src, target, damage, sc->data[SC_WATK_ELEMENT]->val1, tstatus->def_ele, tstatus->ele_lv);
if (is_attack_left_handed(src, skill_id)) {
damage = battle_calc_base_damage(sstatus, &sstatus->lhw, sc, tstatus->size, sd, (is_skill_using_arrow(src, skill_id)?2:0)) * sc->data[SC_WATK_ELEMENT]->val2 / 100;
wd.damage2 += battle_attr_fix(src, target, damage, sc->data[SC_WATK_ELEMENT]->val1, tstatus->def_ele, tstatus->ele_lv);
}
}
You can mess around there if you want to change how it works, but I don't really have time to write you a complete solution for what you want. Maybe if you remove the requirement for there to be wd.damage or wd.damage2 it might work on a miss?